The present invention relates to an intra-liquid particle classification apparatus using light scattering, in which classification and counting of particles are carried out on the basis of an image obtained by light scattering of particles in a liquid sample such as blood, urine, etc.
Such a particle classification apparatus is an apparatus for resting particles in a liquid sample such as blood or urine in a hospital, a testing center, etc. That is, a liquid sample is made to be contained by a sheath liquid serving as an outer layer thereof to form a stationary flow having a flat section, that is, a sheath flow in a flow cell. The liquid sample in the flow cell is irradiated with strobe light of short light-emitting time, then the scattered light is picked up by an image pickup unit to thereby obtain a still frame image. The still frame image is processed in an image processing to thereby classify and count particles in the liquid sample. In most cases, particles suspended in the liquid sample are stained in a stain liquid so as to facilitate discrimination using light scattering.
An example of conventional particle classification apparatuses is disclosed in U.S. Pat. No. 5,088,816. In this particle classification apparatus, a liquid sample is sucked by a determination device so as to be temporarily reserved in a flowing vessel. An electromagnetic valve provided in the flowing vessel is switched so that the liquid sample is led into a reaction vessel by a suction pump. The electromagnetic valve is further switched so that the liquid sample having been reacted is sucked from the reaction vessel by the determination device and introduced into a flow cell. In this occasion, the liquid sample in the flow cell flows from the upper portion toward the lower portion. The liquid sample flowing in the flow cell is periodically irradiated with strobe light, and particles in the liquid sample is image-picked up as a still frame image by an image pickup unit using this strobe light. Then, classification and counting (hereinafter referred to as "test" occasionally) of the particles in the liquid sample are carried out based on the picked-up still frame image. Further, a filter for removing foreign matter such as dust is provided in an upstream portion of the flowing vessel, so that mixed foreign matter is removed by the filter.